Ignition coils are components that use the coupling between a primary winding and a secondary winding to transform relatively low voltages from the battery into high voltages that are supplied to the spark plugs in vehicle gasoline engines. The spark plugs start the internal combustion process that drives the rods and hence, crankshaft and axles. In older systems, a single ignition coil is provided, and a distributor sends the pulses from the coil through respective high voltage spark plug wires to the spark plugs in the cylinders in accordance with a timing that is established by the distributor.
In relatively modern engines, an engine can have several ignition coils, one for each cylinder or for each pair of cylinders, thereby advantageously eliminating the need for distributors and high voltage wires and also providing more precise control of the engine timing. One example of such an ignition coil system is set forth in U.S. Pat. No. 6,556,118, owned by the present assignee and incorporated herein by reference.
When such a coil is used to energize two spark plugs (either for two different cylinders or for a single cylinder in an engine that has two spark plugs per cylinder), two secondary windings surround the low voltage-carrying primary winding that is wound on an interior ferromagnetic core, with the secondary windings being radially spaced from the primary winding. Each secondary winding, owing to the inductive coupling between it and the primary winding and the different numbers of winding turns between the primary and secondary windings, produces a high voltage that is sent to a respective spark plug.
As understood herein, the ends of the secondary windings that are opposite the ends which are connected to the spark plugs must be connected to ground (in a three conductor system) or to the positive pole of the battery in a two conductor system to complete the electrical path. The present invention also understands that if these ends are located axially between oppositely-wound secondary windings, somehow electrical connection must be made from the middle of the ignition coil to the end, for connection to ground or battery positive. As critically recognized by the present invention, owing the relatively small size of modern ignition coils, the space available to run a lead from between the secondary windings and past one of the high voltage secondary windings to an end connector is limited, making electrical connection using a lead internal to the ignition coil difficult and problematic. Having made these critical observations, the invention below is provided.